Joint DOA, DOD, and Range Parameter Estimation for Bistatic FDA-MIMO Radar via Triangular Geometry and Maximum Likelihood Criterion

Accurate multidimensional parameter estimation is fundamental for target localization in bistatic frequency-diverse array multiple-input multiple-output radar systems. A critical challenge in such systems arises from the inherent coupling between direction-of-departure (DOD) and bistatic range sum parameters, which significantly complicates the estimation of target DOD, direction-of-arrival (DOA), and range sum. To address this problem, we propose a two-stage parameter estimation framework: 1) DOA estimation via the maximum likelihood estimator and 2) joint DOD and range sum estimation leveraging the bistatic triangular geometry, the DOA obtained in the first step, and the principal range determined by the target’s range cell. An error propagation function is developed to quantitatively analyze the impact of DOA and principal range estimation errors on DOD accuracy. It is revealed that the DOD estimation error induced by the principal range inaccuracy is negligible compared to that caused by DOA discrepancy. Furthermore, the Cramér–Rao bounds (CRBs) and Ziv–Zakai bounds (ZZBs) for DOA, DOD, and bistatic range sum are derived. While the CRB provides a tight bound only in high-signal-to-noise-ratio regions, the ZZB offers a globally valid performance bound, making it more suitable for a comprehensive performance evaluation of the proposed method. Simulation results demonstrate the effectiveness of the developed estimator and its superior parameter estimation performance compared to competing methods.